Viscous urea-formaldehyde compositions and method for preparing the same



Patented Jan. 13, 1953 UNITED STATES PATENT OF F-ICE VISCOUSUREA-FORMALDEHYDE COMPOSI- TIONS AND METHOD FOR PREPARING THE .SAME

ware

No Drawing. Application December 26, 1951, Serial No. 263,520

'4 Claims.- (Cl. 26029.4)

This invention relates to viscous ureaeformaldehyde compositions and toprocesses for preparing viscous compositionsfrom mixtures of highermethylol ureas and urea. This application is .a continuation-in-part ofmy copending application S. N. 175,470, filed July 22, 1950', nowabandoned. The latter application is a continuationin-part of myapplication S. N. 750,-167, filed May 23, 1-947, now abandoned, which inturn is a con.- tinuation-in-part of my application S. N. 732,927,now-U. S. Reissue Patent'23,174.

A significant recentadvance in the ureaforma'ldehyde resin art has beenthe discovery of clear, liquid polymethylol urea compositions containingcontrolled amounts of free formaldehyde; these compositions areobtainable by reaction between urea and monomeric formaldehyde which iskept substantially free of polymerized formaldehyde molecules bymaintaining the formaldehyde: temperature above about 45 C. from thetime that the said formaldehyde is produced until the time it isconverted to polymethylol. urea. The clear, liquid, permanently stable,unpolymerized urea-formaldehyde compositions thus obtained are high'inconten't of resin-forming ingredients-and are suitable for shipment.in commercial tank car equipment. 'When mixed with urea, these liquidproducts are widely useful in the manufacture of impregnated wood,impregnated paper, lacquers, finished textiles,v etc as disclosed in myReissue Patent 23,174.

For certainspecifi'c uses, partially polymerized ureaeformaldehyde resinintermediates are-more eiiective than the corresponding. monomericmethylolureasc This is-especially true, intheadhesive art, in makingsolid foams, as a bonding resin insawdust'board, and also to a limitedex.- tent inwthemanufacture. of. certain finished textiles, particularlyc'hintz. Because 'ofthe outstanding properties of the liquidcompositions hereinabove mentioned, especially from the standpoint ofsuitability for storage and shipment, and because of the fact thatforthe abovementioned specific applications. a bodied or partiallypolymerized urea-formaldehyde is .de-

sired, a need 'had arisen for a method for con,- verting theabove-mentioned-liquid compositions to partially polymerizedcompositions having viscosities within the range'suitable forsuchappl-ications; It is also necessary that such bodied compositions besuffi-ciently stable to permit practical' utilization thereof.

An object of this invention is to prepare, from a clear, liquid, stable;methylol urea liquid composition, a partially polymerized viscous,liquid, stable urea-formaldehyde composition, suitable for use as anadhesive or in similar applications. Otherobjects of the inventionappearhereinafter.

The aforesaid objects are accomplished in accordance-with this inventionby providing a .proc-. ess for preparing a urea-formaldehyde partiallypolymerized liquid composition which comprises adding ureato a clear,liquid, aqueous polymethylol urea composition having a total free andcombined formaldehyde urea mol ratio (hereinafter called F/U') of 3.511to 8:1, prefer-- ably i: lto ,6 1,,a ratio of combined to free formal.-dehyde Withinthe range of 1:1 to 3:1 (when the F/U ratio is 4.: 1110,6:1) and aurea-formaldehyde content, including the free and combinedurea andformaldehyde, intherange of to-% by Weight, at a -plrl of 3.0 to9.5, until the total free and. combined F/U mol ratio is in the range of1.8: 1 to 3:1, maintaining the resulting mixture at the saidpH at a.temperature of 25 to 110 C., said temperature being however not inexcess of C. when the pH is below 5.0, until the tree formaldehydeconcentration closely approaches, or reaches, a constant, equilibriumvalue as defined: hereinafter in greater detail, thereafter heating themixture at apI-I in the. range. of 3,0 to 6.9 at a temperature in therange of 60 to 110 C., said temperature being however not less than 0.when the pH is within the range. 016.5 to 17016.9, unti-lits viscosityis within the rangeof4O to 3600 oentipoises. If the resulting mixture isto be stored before usage, the pH should preferably be adjusted to avalue within therangezof'loto 9.0.; if the mixture is to beused withinaweek,;it is notnecessa y toadi 11st thepH Moreo t. at

a pH as low as 6.0, storage for about one month is possible.

The ratio of combined formaldehyde to free formaldehyde in the stable,clear, polymethylol urea solutions used in the process of this inventionis generally between 1.0 and 1.8 when the F/U mol ratio is 6:1, while ata F/U ratio of 4:1 the ratio of combined formaldehyde to freeformaldehyde is usually between 1.8 and 3.0.

While it is generally desirable in the manufacture of impregnatingcompositions to employ monomeric methylol ureas (or mixtures of urea andformaldehyde) in which the F/U ratio is relatively low, 1. e., about1.3, a higher F/U ratio is preferred in bodied compositions to be usedin the manufacture of adhesives. The compositions of relatively low F/Uratio are generally not suitable for use in the manufacture of stable,viscous compositions, since the shelf life of the viscous materialsincreases with an increase in F/U ratio. As a rule, the viscouscompositions increase in viscosity on storage until, after severalmonths at room temperature, gelation sets in. When the F/U ratio isbelow 1.8:1, the mixtures become thixotropic in a few days to severalweeks. The preferred viscous compositions, having a somewhat higher F/Uratio, on the other hand, may be stored for about six months or more.Commercial practice apparently requires that such materials remainuseful for a period of at least about two to four months. When the F/Uratio is relatively high, i. e., about 3, the viscous compositions arepermanently stable, but these high ratios are generally above themaximum required for maximum bond strength when the materials areemployed as adhesives. The preferred range of F/U ratio for the bodiedcompositions is thus within the range of 1.8 to 3.0. The optimum rangefor the manufacture of cloudy products of the highest quality, whilestil1 having a shelf life within the acceptable range, is about 1.8:1 to2:1.

The pH of the reaction mixture during the adjustment of the F/U ratioshould be such that extremes of acidity or alkalinity are avoided. Asuitable range of pH is about 3.0 to 9.5. If, during this stage of theprocess, the pH is kept within the range of about 7 to 9, polymerizationof methylol ureas does not take place rapidly. Moreover, the range oftemperatures which may be employed under such conditions is remarkablywide: for example, an experiment was made in which the temperature wasincreased to as high as 400 C. while maintaining the pH of thepolymethylol urea solution at 7.0 to 9.0, the reaction vessel being apressure-resistant autoclave. It was discovered that formaldehyde couldbe withdrawn from the gas phase without polymerization of the liquidcomposition, and that this withdrawal of formaldehyde could be continueduntil the resulting mixture was an aqueous mixture containing nourea-formaldehyde and no free formaldehyde.

While this result shows that the liquid polymethylol urea compositionsdo not polymerize rapidly at elevated temperatures when the pH iscarefully controlled and maintained within the range of 7.0 to 9.0, itis generally preferable (although not essential) to control thetemperature during the adjustment of the F/U ratio in the practice ofthis invention so that it does not exceed about 110 C. The reason forthis is that at temperatures above 110 C., a relatively high pressuremust be employed to keep the formaldehyde from escaping, and since thereaction takes place very rapidly, even at temperatures below 110 C.there appears to be no valid reason for employing conditions which wouldrequire precautions to prevent escape of formaldehyde. A suiiicientlyrapid reaction between the urea and the uncombined formaldehyde takesplace at a temperature as low as about 25 C.

While temperature control is of relatively minor importance when the pHis within the range of 7.0 to 9.0, it is of major importance when the pHis on the acid side and especially when the pH is below 5, i. e., withinthe range of 3.0 to 5.0. Indeed it is essential that the temperature bekept below C. when the pH is within the range of 3.0 to 5.0. Otherwiseresinification takes place very rapidly and viscous liquid compositionsare not obtained.

The reaction between the added urea and uncombined formaldehyde isgenerally permitted to take place until an equilibrium is approached orreached. This can be followed analytically, and the reaction can thus becontinued until the concentration of free formaldehyde becomes constant.This occurs when the free formaldehyde content falls below 3% of theweight of the composition, when the F/U ratio is 1.8 to 2.0. Theequilibrium value is somewhat higher when the F/U ratio is 2.1 to 2.3.An excellent method of operation, if a very stable bodied intermediateis desired, is to body the mixture at F/U 2.3 and thereafter to increasethe F/U ratio to 3 by addition of Arboneeld B (defined hereinafter).

After the adjustment of the F/U ratio, and the reaction between theadded urea and the free formaldehyde as above described, the mixture isheated under acidic conditions until the desired viscosity is reached.During this bodying step, the temperature must be kept sufficiently highto prevent the formation of a thixotropic mixture. In general, thetemperature should be within the range of 80 to 110 C. However, thetemperature must be controlled even more narrowly than this if the pH isnot below 6.5. The control of the temperature and pH during the bodyingstep is highly critical. For example, at a pH of 6.5 a temperature of 80cannot be employed because this gives rise to a thixotropic composition.At a pH of 6.0 and a temperature of 80 C., the bodying reaction takesplace satisfactorily. On the other hand, when the pH is below 5, thepolymerization is too rapid to permit proper control unless thetemperature is below 110 and preferably below about C. In general, thepreferred range is about 80 to 110 0., provided that precautions aretaken to keep the temperature above C. when the pH is within the rangeof 6.5 to 6.9. The bodying reaction is continued until the viscosity isat least about 40 centipoises (25 C.). If desired, the reaction can becontinued until the viscosity is so high that gelation is imminent. Thedanger in permitting the reaction to proceed until the viscosity is sohigh that gelation soon occurs is that the increase in viscosity, as thegelation time is approached, is quite rapid and the reaction istherefore somewhat more difficult to control. Therefore, it is desirableto stop the reaction when the viscosity is somewhat lower than thatwhich indicates imminent gela tion; a suitable upper limit is about 3600centipoises (25 0.).

The rate at which the polymerization takes place depends not only uponthe temperature and pH but also upon the F/U ratio, as illustratedhereinafter in greater detail.

When the desired viscosity is attained, as above aces-s24 .5 described,the pH may be adjusted to aboutIZ-D to 9.0 to produce maximum stability,aiter-which the viscous mixture is cooled to storage.tempera.--

In the various steps described above, control of the pH can beaccomplished by any of the.-

known means for producing a hydrogen-ion concentration within thedesired range. Sufficient.

quantities of phosphoric: acid and/or sodium hydroxide may be employedif desired. Any other buifer mixture which produces the desired pI-I maybe employed; for example, mixtures. of sodium hydroxide and boric acidor other similar buffer mixtures give substantially the same results asare obtained witnthe-phosphoriciacidsodium hydroxide buffer.

The maximum solids content of the-compositions of this invention'(so'lids content" meaning free and combined urea-and HCHO) depends uponthe formaldehyde and water content ofthe aqueous formaldehyde employedin making the initial polymethylol urea solution. Monomeric formaldehydeobtained by the oxidation of methanol contains about 50% to 70% byweight of formaldehyde. The polymethylol urea liquid compositionobtained from crystal urea and this monomeric formaldehyde is mosteconomically employed in the practice of this1iinvention',.'andaccordingly the solids content of. the compositions obtained in thepractice: of this invention is generally in the range of. about 60% to751%.

A typical polymethylol urea liquid. composition which gives excellentresults as'a starting. material in preparingthe compositions. :of thisinvention contains the. following ingredients:

Formaldehyde free and combined) When urea is added to 1000 grams of thismaterial (hereinafter referred to as Arboneeld B) the solids content .isaffected as follows:

Weight urea F/U ratio i g z gs ooigoooo' \xqqq tomcnmq It is to beunderstood however that once the viscous compositions have been obtainedthey can be diluted with water if a composition of lower solids contentis desired. However, when this is done, the viscosity of the compositionis very markedly decreased as. shown in the following table. 'The tableshows the effect of' diluting various bodied compositions obtained inthe practice of this invention, with water from a solids content of '70by weight to a solids content of 50% by weight; This decrease inviscosity is not characteristic of 'any'p'art-icularF/U ratio, but isobserved over a rather wide range of F/U ratios.

.Efiectsoj-concentmtzon on uiscosities of "bodied .-liq zrz'd-Zwear-formaldehyde products %so1ids 50% solids f Ce'ntipoiser'C'entiz'icises' Y p 20 In. some instances, it .is highly desirable .todilute the ibodied'wcompositions in orlder to. ex.- tendtheir storage.life. For exampla. the com.- position having. a viscosity of? .3500.centipoises at ansolids. content". of 70% by weight has a life span ofabout. av month at. room temperature: however, by diluting the mixtureuntil the viscosity is 150 centipoises the .life. is so greatly extendedthat the composition increases in viscosity to only about centipoises inthree months.

One of the most important embodiments of the present invention residesin the production, from Arboneeld B and urea, of viscous clears havingmaximum solids content (F/U ratios of 2.2 to 2.5).. The specificconditions for making such clears" from Arboneeld B and urea depend"upon ('1) F/U ratio, (2) free formaldehyde content at the end of themethylol-forming step, i. e. the methylo-lation of the added urea, (3)pH of the bodying, step, and (4) temperature of the bodying step. Asignificant observation is the discovery that the free formaldehydecontent, after adjustment of the F/U ratio to as IOWI as. 2.2, must becontrolled at a level which dependsuponthe bodying temperature. This isdone by continuing the .methylolation step only until the desired. stageis reached, in accord with the data given below. At F/U ratios below2.2,

viscous clears are rarely obtainable, although and urea at F/U ratiosabove 2.5. As shown in the following. table the content of freeformaldehyde atF/U 2.2-2.3, .requiredfor making clears is, 4.120 5% whenthe budying. temperature is 95 .63.. 85 1C;, .cIears are not thusproduced at this low F/U ratio,-as shown in the table.

Theclarlty of the bodied Arboneeld B-urea depends also-on how far thebodying has been permitted to proceed.

In addition to the foregoing procedures for controlling'the clarity ofthe bodied compositions, it has'been. found that products of the samecomposition can be made by starting with relatively pure dimethylolurea.This is accomplished by mixing dim'ethylolurea at pH of 7 to 9 withmonomeric formaldehydeand water in such proportions that the F/U ratiois 5 and the U-F content is 65%. This mixture can then be heated.at.60-70 untilthe content of free formaldehyde is the same as inArboneeld B. The resulting clear stable compositions can. be convertedtoviscous 'clearsibyadmixing. with urea and carryingout themethylolationand bodyingsteps in the manner hereinabove just described for Arbonee1dBurea.

Table I.E17ect of methylolation conditions bodying temperature onclarity of product from "Arboneeld" B-urea at maximum solids cOntGnt,F/U-2.2-2.3

[In these experiments the "ArboneelrP B-urea methylolation product wasmade by adding urea to Arhonecld B and heating the resulting mixtureunder the specified conditions until the free formaldehyde content fallsto 4.15.6l%, as shown. The pH is then lowered as shown in the table, andthe oodm'ng step is performed] Methylol-forming step Bodying conditionsProduct 4 a as mo so 1 s na added, Temp. 1 Temp. Viscosmm percent 0.rsgnge, 33? pH range gfi range, 3 32 pH range ity cp., gg g 1 percent 252. 71 50 65-70 9 7.4 -8.3 6.06 83-88 60 4. 6 -4.9 435 Opaque. 2. 71 4965-69 22 7. 3 -8. 1 5. 08 83-85 70 4. 65-4. 75 475 Clear. 2. 71 50 65-6832 7. 4 8. 0 4. 30 85 52 4. 60 285 Do. 2- 71 50 65-70 42 7.1 -8.2 4.1284-85 49 4. 70 290 Do. 2. 70 50 65-73 20 8. 28-9. 00 4. 01 84-85 42 4.70-4. 75 225 Opaque 2. 70 50 65-70 71 7. 30-8. 35 3. 76 85-86 534.55-4.82 245 Do. 2. 71 50 65-68 18 5. 20-5. 30 4. 79 85 75 4.70-4.75630 Do. 2. 71 34 60-66 18 7. 40-7. 80 4. 79 80-85 56 5. 00 340 Do. 2. 7155 55-56 76 7. 75-8. 4. 53 90-96 76 5. -5. 240 Clear 2. 71 50 60-66 227. -7. 90 4. 14 80-86 33 4. 85-4. 90 370 Opaque 2. 71 45 34-46 20 8.70-8. 80 5. 60 70-93 00 4. 90-5. 30 320 Do. 2. 71 32 65-66 20 7. 50-8.00 5. 61 02-95 40 '4. 95-5. 20 130 Clear 2. 71 30 65-65 20 7. 60-7. 904. 79 90-96 60 5. 00-5. 10 135 Do 1 Total urea plus free and combinedECHO.

2 Time at the reaction temperature shown in the preceding column. Afteradding the urea the charge was heated rapidly to the reactiontemperature of the methylol-iorming step.

3 Time at the hodying temperature shown in the preceding column. Afterthe methylol-forming step was completed the pH of the charge wasadjusted to the range shown for the bodymg step and the charge washeated rapidly to the bodying temperature.

4 The products listed as clear have remained clear on storage at 25 C.at pH of 7-9. The age of the products varies from three to sixteenweeks. When clears are unstable a precipitate usually forms within oneweek.

The invention is illustrated further by means of the following examples.

EXAMPLE 1 Typical procedure to body "Arboneelcl B-urea compositionsusing intermittent pH control cosity 22 centipoises at 25 0.; pH, ca. 7)is added 5:

to a 2-liter, 4-neck flask fitted with condenser, stirrer andthermometer. The pH is adjusted to 8.0 using 4% sodium hydroxide. To theresulting mixture is added 185 grams of urea to form a solutioncontaining 39.3% total formaldehyde, 31.3% urea and having aformaldehyde to urea mol ratio of 2.5. The mixture is heated to 100 C.in 16 minutes by use of a Glas-Col mantle. After 10 minutes at 100 C.there is added 20 milliliters of 0.5% hydrochloric acid and the pHdecreases to 5.0 as determined with a Beckman Model G pH meter on asample of the charge cooled to room temperature. Heating is continued at100 C. for 130 minutes during which time the viscosity increases from 50centipoises to 135 centipoises measured at 25 C. There is then added 3.5milliliters of 4% sodium hydroxide and the prodnot is cooled to roomtemperature. The pH is then 7.3 and 0.5 milliliter additional sodiumhydroxide is added to adjust the pH to 8.0. After the final pHadjustment, the concentration of combined urea and formaldehyde plusfree formaldehyde is 69% and the viscosity is 130 centipoises. Onstorage at room temperature for four months, the viscosity increases to235 centipoises and the product remains clear.

EXAMPLE 2 Typical procedure to body Arboneeld B-urea compositions usingcontinuous pH control -in a 5-liter, 4-neck flask fitted with condenser,

stirrer, thermometer and an assembly of high pensating resistancethermometer.

temperature pH electrodes together with a com- The electrodes and theresistance thermometer are connected through a switch box to acontinuously indicating Beckman Model R pH meter. The charge is heatedto C. in 30 minutes and then maintained at 80 C. for 25 minutes. The pHis held in the range 7.8-8.0 by the addition of 20% sodium hydroxide. Atthe end of this alkaline heating period the free formaldehyde content isless than 2%. The pH is then adjusted to 5.0 by the addition of 0.5%hydrochloric acid and the heating is continued at 80 C. The chargebecomes opalescent in about 5 minutes after the addition of thehydrochloric acid and remains opalescent. After heating at 80 C. forminutes the solution is made alkaline by the addition of 20% sodiumhydroxide and cooled to room temperature. The product has a pH of 7.5,the viscosity is 450 centipoises at 25 C. and total formaldehyde plusurea is 70.9%. On storage at room temperature the liquid increases inviscoiity and after about four months sets to a ge EXAMPLE 3 Procedureto body a mixture of higher methylolurea and urea (F/U 2) One thousandgrams of a higher methylol urea containing 50.8% total formaldehyde,13.0% urea (F/U ratio 7.8) and 378 grams of urea were added to 2-liter,4-neck flask fitted as described in Example 2. The pH was adjusted to 8and the mixture was heated to 103 C. After 7 minutes at this temperaturethe pH was adjusted to 5.35 and heating was continued at 99 C. for 33minutes. The charge was made alkaline and cooled to room temperature.The product had 2. UP solids content of 71.2% and F/U ratio 2.0. Theviscosity was 450 centipoises, the pH 7.8, and the material was clear.

EXAMPLE 4 Rate of bodying of Arboneeld B-urea (F/U 2.5) A mixture of1000 grams of Arboneeld B and 185 grams of urea (F/U 225). was heated atpH 7.9 -for 10 minutes as described in lilxarnple 1. The somtionwas thenadjusted to pH 5.0 with 0.5% hydrochloric acid and heating was continuedat 100 C. Samples of the charge were takenliperiodically for viscosity"measurements at 25 C. The rateof increase of viscosity was as follows:

Test '1, in the table -presented below, shows whatv happens when urea isdissolved in fAr; boneeld B and the alkaline solution-hallowed to"standgat room "temperature. Prior to solidificationthis material is amoderately'good adhesive, particularly onthe denser. woods. 'On -lowdensity woods use of fillers or thickening "agents improves theperformance of theadhesive.

Effect of viscosity on stability of bodied -u li'boizcelcl itfeuQF/UQ) 1. Test number 1 2 3 4 5 t t e p Bodymg step:

D (2) Temp, (3) Tlme, mins 5 Product:

(1) Adjusted a (2) Visc., cp. C- v (3) Appearance 6. Storage properties,room temperature.

Opaque.

1 solidifies in 16-48 hours.

i Becomes opaque on cooliiig't'd'wfCi 'Fcrmsathisotropic'gelin1'648hcurs a Becomes thixotropic gel 'withina week. 4 Becomes a thixotropicliquid in 2 weeks.

5 Viscosity increased to 240 cp. in 2 weeks. Viscosity increased to 250cp. 111 2 weeks. 1 Viscosity increased to 340 cp. 1n 2 weeks.

Ppt. present. Pptnpriasent... Trace of ppt. present. corresponding tosome fcommerci ballets.

l Viscosity increased to 1800 cp. in 2 weeks. Traceoflpptupresutcorrespondingto-some commereial products.

Minutes. at .pH -5 Viscosity, and 100 C. cp.; 25C.

400 gel Minutes'atpHB and oqi 0. required "to produce gelsl- -tion;

Minutes at pH 6.9 and 100 C. required to produce gelation, 2,500.

EXAMPLE 5 change in the analysis for free formaldehyde.

The eiiect of temperature on the time required for the free formaldehydeto decrease to less than 3% during the methylol-forrni-ng step at pH 7.6in reacting Arboneeld B-urea of F/U 2.0 is shown below.

Time for free formaldehyde tode'cr'as'e below 3% Temperature, C.

16 hours. 30 minutes.

10 minutes.

v 6. Viscosity on storage at f Product:

Tes't'2 the iiiciease' ih'tiisctsity or; teating out themethylol-forming step. This product, prior to gel formation,haSfiflcts'tantially the same a'dhesive properties as the 'un'ra'ctedArboneeld B u'rea ot test As' the viscosity increases in the lower rangethe storage stability improves: At man s- 5 mma eri forms a-eel Withiaweek (test-3)"; aft TOOb'eiit as at "tare liquid for in awe Weeks"(test-,4); whereas at I45 centipe'ises and nieher'visccsitiestheproducts do not give rise to these difliculties.

This exam m shows the effects er niitting the m'thyi r-rdrfming stepb''fdr'e a cut the acidic or bod-ying reaction; -In test 1 the methylolfor'riiing (step was included. A clear product was obtained. In test 2the marina: forming step was omitted and an opaque product was formed.'qnstdrage'atroomtemperature the opaque product increased in Viscosityeaasi'd'e'r ably faster thanthe clear product.

1. Test nl i'mlier 1 2 e Adjusted 311-. (2) Visc., cp. 25 C temperature,I

time. a moon.

I The effedt or F/U ratio on thebbeyiiig rate are on the clarity 'anavstabm or t 'iir iict bodied at c. and pH-about =5 shown xample 11' 12 7.The example shows that the higher the F/U EXAMPLE ratio, the slower thebodying rate, and the longer the stora e life of the product. At F/U 3.5(test E17 ect of 322 ;222: 5? 12K gfig g gf bodied 6) the products aresubstantially permanently stable, whereas below F/U 2.0 the stability of5 The material described in test 3, Example 7, the product is relativelypoor. The example also was stored at -25 C. for three months (pH 7.6)shows that temperature has a marked effect on at which time theviscosity was 570 centipoises. the bodying rate and the stability of theproduct. A portion of the product was then stored at C.

Effect of F/U ratio on rate of bodying of "Arboneeld B-urea and onclarity and stability of the product 1 Viscosity increased to 380 cp. in2 weeks. A slight ppt. formed. Used to prepare adhesive, Test 1. Example12.

2 A clear gel formed in 3 months. 3 Viscosity increased to 700 cp. in 4months. Product clear. Viscosity increased to 235 cp. in 4 months.Product clear. Viscosity increased to 110 cp. in 4 months. Productclear. Viscosity increased to cp. in 4 months. Product clear.

EXAMPLE 8 The changes in viscosities of the two samples The effect ofbodying temperature on the propwere as follows: erties of viscousArboneeld B-urea compositions 35 is shown in the following table.

Storage temperature 2025 C. 50C. Effect of bodying tempemture onproperties of viscous "ArboneeloV B-urea compositions Viscosity, cp. 250.

1. Test number ..l 1 I 2 3 4 2. F/U ratio ofchsrge 2.5 2.5---. 2.5. 2.5.3. Methylol-forming step:

1 Temp.,0..--.. e5 75.-- 90 mo. 2 7.4 7.1---- 7.0---- 7.9. 4. Boclyingstep:

1 pH 5. 0. 2; $emp.,0.-. 3 ime,mins.-.. 5. Product: EXAMPLE 11 (l)AdjustedpH..-" 8.1 7.5.--- 7.8.-.- 7.9. (2)Visc.,cp.25C..-- s5 100....190.... 130. (3) wrenches fi 3 50 pl of Arboneeld"B-urea (F/U 2.5) wassmmge pmpemes' O U U U bodied 1to 1'75 centipoises using the procedureof Examp e 2. Portions of this sample were then 1 A precpme formed in 3days adjusted to difierent pH levels and stored at room I A precipitateformed in 3 days.

, Viscosity increased to 385 op. in 4 months. Product clear.

4 Viscosity increased to 175 cp. in 1 month. Product clear. Used 55 toprepare adhesive, Test 2, Example 12.

EXAMPLE 9 Effect of pH on rate of hedging of Arboneeld B-urea (F/U 2)a 1. Test number 1 V 2 3 4 5 6 2. F/U raltilo ofcharget. 2.0 2.0.-..-2.0 2.0 2.0.... 2.0. 3. Mom o-formin se i y Temp., C 8O 80.....1; 80 8080.

(2) pH 7. 8. 8. 8. 8.0 8.7. 4. Bed in ste (2) Temp.,C.... 80 so so so.

(3) Time, mins.,ca 15 350 610 240. 5. Product:

(1) Adjusted pH 8-2 8.2.----- 7.6..---- 7.6.

(2) Visc.,cp.250 20 200 200 200 200.

Appearance... Opaque. Opaque. Opaque. Opaque. Opaque. Opaque. 6. Storageproperties, r. t

1 Trace of ppt. formed in 2 weeks. Similar to some commercial products.

1 Slight amount of ppt. formed in 2 weeks. I Large amount of ppt. formedin 2 weeks. 4 Set to a thixotropic gel in 1 day.

accuse is temperature. The storage properties are given below:

Storage pH Storage properties atroom temperature Gelled in 1 week.

Gelled in 2 weeks. 275 cp. in 1 month. 200 cp. in 1 month. 205 cp. in .1month. 2400p. in 1 month.

EXAMPLE 12 Test 1.-The product for test '1, Example '7 (aged one week;viscosity about 330 centipoises; opaque; F/U 1.8), was used to preparean adhesive. To 100 grams of the intermediate there was added 20 gramsof walnut shell flour filler and 0.7 gram of ammonium chloride catalyst.This was then applied within 5 minutes to both sides of a x 12/12" dryDouglas fir veneerby means of a brush. The application rate was 85pounds of liquid glue per 1000 sq. ft. of single glue line. A plywoodbundle was then formed by placing the core between two Duglas firveneers. After standing 5 minutes the assembly was pressed at 135 C. and150 p. s. i. for 15 minutes. The pot life of the adhesive at roomtemperature was 55 minutes. Plywood shear-strength specimens from thepanel were tested dry, and the break occurred within the wood ratherthan in the adhesive bond; specimens were boiled in waterfor 4 hours and6 of the specimens delaminated. In a similar test with a urea-formalinmixture (F/U 2.0) steam blisters developed and a poor bond was obtained,due to the relatively low solids content. The content of total solidswas increased by adding wheat flour, and this avoided the blisters butproduced a poor bond. When the solids content was increased by vacuumdistillation of water good bond strength was obtained with dryspecimens, and in the boiling water test 8 of 10 specimens delaminated.

Test 2.-An adhesive was prepared from the product of test 4, Example 8by adding 7.8 grams of urea to 100 grams of the composition having anF/U of 2.5 to obtain F/U 2.0, and allowing the mixture to standovernight. There was then added 20 grams of walnut shell flour and 0.7gram of ammonium chloride. A Douglas fir plywood panel was prepared asdescribed in test 1 and shear specimens were boiled in water for 4hours. None of the 10 specimens delaminated. The pot life of thisadhesive was 70 minutes.

Test 3.-A clear Arboneeld B-urea composition having an F/U ratio of 2.5and a viscosity of 120 centipoises was used to prepare an F/U 2 adhesiveas described in test 2 except that the catalyst was added at the sametime as the urea. In this case also there was no delamination of theshear specimens on exposure to boiling water for 4 hours. The pot lifeof the adhesive was 145 minutes.

Test 4.-Test 3 was repeated except that the mixture of F/U 2.5 and ureawas heated at 85 C. for 20 minutes and cooled to room temperature beforeadding the catalyst. There was no delamination in the boiling watertest. Pot life of this adhesive was 105 minutes.

Test 5.An adhesive was prepared from an opaque Arboneeld B-ureacomposition having an F/U ratio of 2.0 and a viscosity of 450centipoises. To 100 grams of the basethere was added 20 grams of walnutshell flour and 017 gram of ammonium chloride catalyst. This was spreadat the rate of 79 pounds of liquid adhesive per 1000 sq. ft. of singleglue line in preparing a three ply 12" x 12 panel Hom birch veneer. Thepanel was pressed at 135 C. and 150 p. s. i. for 20 minutes. Shearspecimens were th'en boiled in water for 4 hours and there were nodelaminations.

The above examples serve to illustrate theinven'tion and to point outcertain of the advantages thereof.

The viscous Arboneeld -B-'-urea compositions obtained as above describedare suitable fonu'se in all applications where standard viscousureaformaldehyde liquids are employed. There'su-l'ts obtained with thesecompositions 'as plywood'adhesives are quite similar to the results obtalned with the best previous-ly'k-nown urea-formaldehyde adhesives. InExample 12, test-'1 shows the results using an opaque composition-ofF/U' 1.8 on Douglas fir, and test 5 of Example 12 shows the use of anopaque composition of F/U 2.0 with birch. 1 Tests 2, 3 and 4 of thesample example show three procedures for preparing adhesives from clear,bodied compositions of F/U 2.5. In test 2 themixture was allowed tostand overnight at room temperature to react the urea and freeformaldehyde. 'In test "3 the mix was used without first reacting theadded ureain a separate step. In test 4 the F/U 2.5 urea composition washeated with urea at 85 C. for 20 minutes to carry out a methylol-formingstep. Adhesive results by these three routes for converting F/U 2.5 toF/U 2 were all excellent.

From the foregoing specification it is apparent that by using excessformaldehyde in uncombined form with higher methylol ureas, andthereafter bodying the mixture as described herein, the storage life ofthe adhesive is greatly increased and a simple method for preparing ahigh quality adhesive is provided. One of the surprising features of theinvention is that despite the stabilization which is efiected throughthe use of polymethylol ureas and controlled amounts of freeformaldehyde the steps of preparing a satisfactory bodied adhesive fromthe permanently stable composition are not unduly difiicult or complex.

I claim:

1. A process for preparing a urea-formaldehyde partially polymerizedliquid composition which comprises adding urea to a clear, liquid,aqueous polymethylol urea composition having a total free and combinedformaldehyde urea ratio of 4:1 to 6:1, a mol ratio of combined to freeformaldehyde within the range of 1:1 to 3: 1, and having aurea-formaldehyde content including the free and combined urea andformaldehyde in the range of 60% to at a pH of 3.0 to 9.5, until thetotal free and combined formaldehyde urea mol ratio is in the range of1.8:1 to 3:1, maintaining the resulting mixture at the said pH at atemperature of 25 to 110 C., said temperature being however not inexcess of C. when the pH is below 5.0 until the free formaldehydeconcentration decreases to a constant equilibrium value, and thereafterheating the mixture at a pH in the range of 3.0 to 6.9 at a temperaturein the range of 60 to 110 C., said temperature being however not lessthan C. when the pH is within the range of 6.5 to 6.9, until itsviscosity is within the range of 40 to 3600 centipoises.

2. A process for preparing a urea-formaldehyde partially polymerizedliquid composition which comprises adding urea to a clear, liquid,aqueous polymethylol urea composition having a total free and combinedformaldehyde urea mol ratio of 4:1 to 6:1, a mol ratio of combined tofree formaldehyde within the range of 1: 1 to 3:1, and having aurea-formaldehyde content including the free and combined urea andformaldehyde in the range of 60% to 75%, at a pH of 3.0 to 9.5, untilthe total free and combined formaldehyde urea mol ratio is in the rangeof 1.8: 1 to 2:1, maintaining the resulting mixture at the said pH at atemperature of to 110 0., said temperature being however not in excessof 80 C. when the pH is below 5.0, until the free formaldehydeconcentration decreases to below 3% of the weight of the composition,and thereafter heating the mixture at a pH in the range of 3.0 to 6.9 ata temperature in the range of 60 to 110 C., said temperature beinghowever not less than 90 C. when the pH is within the range of 6.5 to6.9 until its viscosity is within the range of to 3600 centipoises, andthereafter adjusting the pH of the resulting mixture to a value withinthe range of 7.0 to 9.0.

3. In a process for preparing a urea-formaldehyde partially polymerizedliquid composition which remains clear on standing at 25 C. for at leastsix months, the steps which comprise adding urea to a clear liquidaqueous composition consisting essentially of by weight oftrimethylolurea, 20% free formaldehyde and 35% water, in sufiicientquantity to produce a total formaldehyde urea mol ratio of 2.5:1 to22:1, subjecting the resulting mixture to a methylolation reaction byheating at a pH of 7 to 9 until the free formaldehyde content decreasesto a level between 4% and 6% of the weight of the mixture, said heatingbeing at a temperature within the range of to 100 0., said methylolationreaction being thus continued until the resulting mixture, uponadjustment of the pH to a value within the range of 4.5-5.0 and heatingat a temperature within the range of to C. until the viscosity reachesto 1000 centipoises, remains clear on standing at 25 C. for a period ofat least 6 months at a pH of 7 to 9.

4. A clear liquid partially polymerized methylol-urea composition havinga pH of 7 to 9, a viscosity of 100 to 1000 centipoises, a totalformaldehyde urea mol ratio of 2.2 to 2.5, a ureaformaldehyde content of65 to 75%, a free formaldehyde content of 2 to 6%, the remainder of themixture consisting substantially entirely of water, said compositionbeing further characterized in that it remains clear on storage for aperiod of over 6 months.

HAMLINE MONROE KVALNES.

No references cited.

1. A PROCESS FOR PREPARING A UREA-FORMALDEHYDE PARTIALLY POLYMERIZEDLIQUID COMPOSITION WHICH COMPRISES ADDING UREA TO A CLEAR, LIQUID,AQUEOUS POLYMETHYLOL UREA COMPOSITION HAVING A TOTAL FREE AND COMBINEDFORMALDEHYDE: UREA RATIO OF 4:1 TO 6:1, A MOL RATIO OF COMBINED TO FREEFORMALDEHYDE WITHIN THE RANGE OF 1:1 TO 3:1, AND HAVING AUREA-FORMALDEHYDE CONTENT INCLUDING THE FREE AND COMBINED UREA ANDFORMALDEHYDE IN THE RANGE OF 60% TO 75%, AT A PH OF 3.0 TO 9.5, UNTILTHE TOTAL FREE AND COMBINED FORMALDEHYDE: UREA MOL RATIO IS IN THE RANGEOF 1.8:1 TO 3:1, MAINTAINING THE RESULTING MIXTURE AT THE SAID PH AT ATEMPERATURE OF 25* TO 110* C., SAID TEMPERATURE BEING HOWEVER NOT INEXCESS OF 80* C. WHEN THE PH IS BELOW 5.0 UNTIL THE FREE FORMALDEHYDECONCENTRATION DECREASES TO A CONSTANT EQUILIBRIUM VALUE, AND THEREAFTERHEATING THE MIXTURE AT A PH IN THE RANGE OF 3.0 TO 6.9 AT A TEMPERATUREIN THE RANGE OF 60* TO 110* C., SAID TEMPERATURE BEING HOWEVER NOT LESSTHAN 90* C. WHEN THE PH IS WITHIN THE RANGE OF 6.5 TO 6.9, UNTIL ITSVISCOSITY IS WITHIN THE RANGE OF 40 TO 3600 CENTIPOISES.
 4. A CLEARLIQUID PARTIALLY POLYMERIZED METHYLOL-UREA COMPOSITION HAVING A PH OF 7TO 9, A VISCOSITY OF 100 TO 1000 CENTIPOISES, A TOTAL FORMALDEHYDE: UREAMOL RATIO OF 2.2 TO 2.5, A UREAFORMALDEHYDE CONTENT OF 2 TO 65 TO 75%, AFREE FORMALDEHYDE CONTENT OF 2 TO 6%, THE REMAINDER OF THE MIXTURECONSISTING SUBSTANTIALLY ENTIRELY OF WATER, SAID COMPOSITION BEINGFURTHER CHARACTERIZED IN THAT IT REMAINS CLEAR ON STORAGE FOR A PERIODOF OVER 6 MONTHS.